Electricity 5E using Kill-A-Watt Meters

Updated Spring 2019!

This year, I revised my Kill-A-Watt lab with a lot more math, better leading questions to help students to figure out the concepts, a phenomena that is referenced throughout and an Evaluate with solutions. The lab with an answer key can be found here.

Students always need more math and so this updated version has more calculations based around different strands of Christmas Lights. It brings in the concept that cheaper devices break more often and have more economic consequences as well as being more expensive in the long run. 

The math is challenging for students. They needed some scaffolding and we worked through the first part of #17, 18 and 19 together.

I added an “Evaluate” section which has students find solutions to reducing energy. This is surprisingly tricky for students. The question asks them to find ways to REDUCE energy use. Kids automatically think solar and wind and electric cars. None of these reduce energy–just switches to a more sustainable form. Kids need to learn to answer the prompt carefully.

Bar graph of the wattages of various appliances and electronic devices.

In addition, I added a video at the beginning to engage students as a short phenomena–admittedly its not a great phenomena in the idea NGSS way, but it is really engaging, makes students confused and helps bring together some difficult concepts. I refer to it several times throughout the lab. Note: It is a strange video and a little shocking for students. The link is on the answer key in the lab. Use your own discretion on whether to keep it or not. I found it effective to help students understand a lot of concepts about developing countries, tourism, energy etc.

Original Post

Recently, I received a grant for Kill-A-Watt meters and implemented this new lab.  It teaches students about electricity, watts, math and conservation using Kill-A-Watt meters. The kids were SUPER engaged (so were adults who came by) and it was highly relevant for not only their lives, but the energy concepts they need to know.  My AP® Environmental Science students did the lab, but the AP® Physics B teacher will also use this year.

Click for a copy of the lab.

You will need to alter the copy to reflect the cost of electricity in your town and the specific appliances that you have or want to use in lab.

Supplies Needed

  • Kill-A-Watt Meters:  I had one meter per lab table with two items to test at each table.  I ordered the Kill-A-Watt EZ model from Amazon.  But, I also like the regular model too.   The EZ model lets kids see the cost of electricity more easily, but the regular model is easier to use and find the “watts”setting.  Either are fine for this lab. (But, if you use my write-up, be sure to change some of the instructions if using the regular model).

In order to afford 10 of them, I wrote a grant request on Donors Choose and was funded in a few days by two corporate sponsors.  Here is a post about my favorite ways to find funding for new labs. 

  • Various appliances from your science room or from home.
  • Power Strips (optional).  The plugs in my lab are on the sides of the tables so I found power strips were very helpful. That way all the kids in a group could see the meter when it was plugged in.  I ordered a few of these to have ready next year.  If your’e writing a grant, be sure to add a few of these, if needed in your lab.
    The plugs in my lab are on the sides of the tables which means only 1 person out of 4 could see the meter AND they’d have to turn sideways to do it. Instead, I placed a powerstrip on each table to bring the meter to the top and all kids could read the meter.
  • Christmas lights (optional, but really engaging for the kids) .  I was fortunate to find regular and Energy start Christmas lights at Target in October, but I couldn’t find LED lights so I ordered online.  They were pricey, but I only needed 1 strand and it will last for several years for this lab. (And I can use to decorate my classroom for Christmas!)
    LED, Energy Star, and regular Christmas lights. All were 100 count strands for comparison.

Lab Setup

I had two devices per lab table and meter.  The students rotated from table to table.  I utilized items in the lab whenever possible, like this TV.

The two appliances at this station were the mounted TV and a portable heater.
Large and Small Battery Chargers. The larger one drew more watts, but is also a rapid charger.
Safety warning for the space heater. The heater isn’t dangerous as it has safety mechanisms, but I put a note on just as a precaution.
Apple phone charger and a Micro USB charger. The kids plugged in their own phones. They needed to try two different devices.  Some groups only had iPhones so they had to compare models.
Goggles sterilizer and microwave. It was interesting that the goggles sterilizer (UV light) used the same wattage when plugged it whether it was turned on or off.
A blow dryer on high, low, hot and cold made interesting data.

Data-Explore section

Students took data on a chart and then created a graph.  I had a Kill-A-Watt meter set up at each lab table along with 2-3 appliances and then set a timer for kids to rotate every 4-5 minutes.  I had 9 tables and it took about 45 minutes to rotate to every table.

If kids finished that station before the timer, they worked on the bar graph of their data chart.

The LED desk light only drew 2.8 Watts

Explain-Vampire Power and Conservation

I showed a couple of videos helping explain some of the data that kids see.  I wanted them to notice the appliances that still drew power even when not turned on.  Many students have never heard of this.  I also wanted them to see good examples of energy conservation.

Elaborate–Math Calculations

Kids did A LOT of practice with energy math–which they need for the AP® Exam.  It is also needed in real life.  In addition, they discussed the environmental and human health costs of electricity.

Evaluate-Providing Solutions

Students need a practice in this for the new FRQs in 2020. This is surprisingly tricky for students as they often don’t answer the specific question. 

Students need to think of three ways to conserve electricity or energy in each of the following categories. Remember CONSERVING energy is not replacing it with solar, wind, electric cars etc. Replacing with solar, wind, etc. uses the same amount of watts, but in a more sustainable way.

This video has some ideas (warning, the last few seconds are a little racy) 


Students also referenced Disneyland’s energy website: https://publicaffairs.disneyland.com/environment/energy-conservation-and-emissions-reduction/

* AP® is a trademark registered and/or owned by the College Board which was not involved in the production of, and does not endorse this site.


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